Semiconductor devices, including integrated circuitry, are mass produced by fabricating hundreds or even thousands of identical circuit patterns on a single semiconductor wafer or other semiconductor substrate using photolithography in combination with various other processes. In recent years, research to increase the density of semiconductor devices in a semiconductor assembly has increased. One technique to increase the density of semiconductor devices in a semiconductor assembly is to stack multiple semiconductor substrates upon one another. Through-substrate interconnects are formed through the semiconductor substrates to provide a conductive pathway from an active surface of one of the semiconductor substrates to the semiconductor substrate's back surface to enable interconnection with another semiconductor substrate or a carrier substrate.
An example of a currently available design for a semiconductor-device assembly that utilizes through-substrate interconnects is shown in FIG. 1. As shown in FIG. 1, a semiconductor-device assembly 100 includes a thinned semiconductor substrate 102, a thinned semiconductor substrate 103, and a carrier substrate 104, each of which may be electrically interconnected to each other. The semiconductor substrate 102 includes an active surface 106 and an opposing back surface 108. A number of active semiconductor devices (e.g., transistors) are formed under the active surface 106 and passive components (e.g., capacitors, resistors, or other components) may be formed on or under the active surface 106. Through-substrate interconnects 110 and 111 are formed by filling openings formed in the semiconductor substrate 102 with an electrically conductive material 112. Each of the through-substrate interconnects 110 and 111 also includes an insulating layer 114 that electrically isolates the through-substrate interconnects 110 and 111 from the semiconductor substrate 102. A conductive line 116 electrically couples the conductive material 112 in a corresponding through-substrate interconnect 110 and 111 to a corresponding contact region 118 electrically connected to active devices and/or passive components of the semiconductor substrate 102.
The semiconductor substrate 103 also includes an active surface 122 including active semiconductor devices formed thereunder and an opposing back surface 124. The semiconductor substrate 103 further includes through-substrate interconnects 126, each of which includes an opening filled with an electrically conductive material 130 and an insulating layer 132 that electrically isolates the through-substrate interconnects 126 from the semiconductor substrate 103. Contact pads 134 electrically connect each of the through-substrate interconnects 126 of the semiconductor substrate 103 to a corresponding through-substrate interconnect 110 of the semiconductor substrate 102. Active devices and/or passive components of the semiconductor substrate 103 are electrically coupled to a conductive line 136 through contact region 137. Additionally, a contact pad 135 is also electrically coupled to the through-substrate interconnect 111 and the conductive line 136. Thus, active devices and/or passive components of the semiconductor substrate 103 can be electrically connected to active devices and/or passive components of the semiconductor-substrate 102 by electrically coupling the through-substrate interconnect 111 to the conductive line 116 and the contact pad 135.
The carrier substrate 104, which may be another semiconductor substrate or other substrate, includes terminal pads 142 that are electrically connected to circuitry (not shown) of the carrier substrate 104. Each of the terminal pads 142 is electrically connected to a corresponding through-substrate interconnect 126 by, for example, contact pads 146 and, thus, electrically connected to active devices and/or passive components of the semiconductor substrate 102. Accordingly, a number of different semiconductor-device assemblies may be formed by appropriately stacking and electrically interconnecting semiconductor substrates using through-substrate interconnects.
In order to conserve space on a semiconductor substrate for semiconductor devices, the through-substrate interconnects can be formed with a high-aspect ratio, such as a depth-to-width ratio of 10:1 or greater. However, high-aspect ratio through-substrate interconnects that are consistently and completely filled with conductive material can be difficult to form. FIGS. 2A through 2C illustrate one of the problems encountered when attempting to form high-aspect ratio through-substrate interconnects. As shown in FIG. 2A, a semiconductor substrate 150 including an active surface 152 and an opposing back surface 154 is provided. Openings 156 may be formed in the semiconductor substrate 150 to an intermediate depth from the active surface 152 by etching or by laser drilling. Sidewalls 155 and base 157 of each of the openings 156 may be coated with an insulating layer 158 to electrically isolate conductive material filling the openings 156 from the semiconductor substrate 150. When the openings 156 are subsequently attempted to be completely filled with a conductive material using a deposition process, such as an electrochemical deposition process or a physical deposition process, the conductive material may not completely fill the openings 156.
As shown in FIG. 2B, the conductive material 160 may nucleate, initially, on both the sidewalls 155 and base 157 of the openings 156. As shown in FIG. 2C, deposition of the conductive material 160 proceeds, with the conductive material 160 advancing inwardly until mouths of the openings 156 prematurely close, preventing complete filling of the openings 156 and forming voids 162. Therefore, the incompletely filled openings 156 cannot be reliably and reproducibly configured as low-resistance through-substrate interconnects, as shown in FIG. 1, for electrically connecting active devices and/or passive components of the semiconductor substrate 150 to another semiconductor substrate and/or carrier substrate stacked with the semiconductor substrate 150. Accordingly, researchers and developers of semiconductor devices continue to seek improved techniques for forming through-substrate interconnects in which openings formed in semiconductor substrates are consistently and substantially filled with conductive material.